From: "Serge Kanilo" Subject: Re: URGENT algorithm for the generalized Schur decomposition (QZ) Date: Mon, 27 Dec 1999 07:17:15 GMT Newsgroups: sci.math.num-analysis As I recallthe QZ algorithm at first reduce matrices to Shura form - A - triangular, and B - triangular with additional underdiagonal. It can be done with rotations or reflections. Second step - rotation to reduce B underdiagonal elementes. It is iterative process, alike common QR algorithm, and you must maintain triangularity of A, and watch for diagonal 2x2 blocks - they can contain complex eigenvalues. There was book containing the algoritm in Algol 60 and it description. But unfortunately I forgot the title and names of both authors. Serge Kanilo "Dominique ALLAIN" wrote in message news:386695B5.B8D6F98B@club-internet.fr... > If we have A,B square matrices, then there exist unitary matrices such > that QAZ and QBZ are upper triangular. > > I can't find an algorithm which could give me these two matrices !!! > > Thanks a lot for your help > > Guillaume >